U.S. patent number 5,046,258 [Application Number 07/305,345] was granted by the patent office on 1991-09-10 for wrapping machines.
This patent grant is currently assigned to Molins PLC. Invention is credited to Michael J. Cahill, Dennis Hinchcliffe, Jeffrey J. Patchett, Geoffrey W. Vernon, Peter White.
United States Patent |
5,046,258 |
Cahill , et al. |
September 10, 1991 |
Wrapping machines
Abstract
A wrapping machine, particularly for wrapping cigarette packets
in wrapper film, includes a series of endless band conveyors (148,
152, 156, 166, 170) carrying pushers (150, 154, 158, 172) for
moving successive packets (191) along a straight wrapping line. One
of the pushers (158) is heated to seal a wrapper seam. Opposed
heated band conveyors (166) simultaneously seal end folds of the
wrapper. Packets are gripped between opposed conveyors (145, 148)
immediately after intercepting a wrapper (100). Partially-wrapped
packets are arranged to slide relative to surfaces (149, 153, 157,
180) to attain wrap tightness. Successive conveyors (e.g. 156, 170)
are independently driven to allow phasing of the conveyors to vary
the position at which packets are transferred between them.
Inventors: |
Cahill; Michael J. (Coventry,
GB2), Hinchcliffe; Dennis (Orpington, GB2),
Patchett; Jeffrey J. (Coventry, GB2), Vernon;
Geoffrey W. (Coventry, GB2), White; Peter
(Bristol, GB2) |
Assignee: |
Molins PLC (Milton Keynes,
GB2)
|
Family
ID: |
10631395 |
Appl.
No.: |
07/305,345 |
Filed: |
February 2, 1989 |
Foreign Application Priority Data
|
|
|
|
|
Feb 10, 1988 [GB] |
|
|
8802973 |
|
Current U.S.
Class: |
530/230; 53/206;
53/387.4; 53/228; 53/441 |
Current CPC
Class: |
B65B
51/18 (20130101); B65B 11/12 (20130101) |
Current International
Class: |
B65B
11/06 (20060101); B65B 11/12 (20060101); B65B
51/10 (20060101); B65B 51/18 (20060101); B65B
011/06 () |
Field of
Search: |
;53/133,206,228,230,388,441 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Bray; W. Donald
Attorney, Agent or Firm: Smith, Jr.; John C.
Claims
We claim:
1. A wrapping machine for wrapping articles in succession
including:
means for conveying said articles in succession and in spaced
relationship at a predetermined speed along a path,
means for delivering wrappers in succession to said articles,
including means for locating a first part of each said wrapper with
respect to one of said articles moving on said path whereby each
wrapper is associated with an article, and
means adapted to cause relative movement of a second part of the
wrapper with respect to the associated article so as to cause the
wrapper to be tightened around at least part of the article,
said means adapted to cause relative movement of the wrapper
comprising means providing at least one surface, adapted to move
generally in the direction of said path at a speed which differs
from said predetermined speed of said article, for engaging said
second part of said wrapper, said at least one surface being
adapted to provide sufficient friction between said at least one
surface and said second part of said wrapper to cause drag on said
second part of said wrapper.
2. A wrapping machine as claimed in claim 1, wherein the locating
means comprises part of said means for conveying the article along
said path.
3. A wrapping machine as claimed in claim 2, wherein the locating
means comprises a pusher.
4. A wrapping machine as claimed in claim 2, wherein the locating
means includes means for wrapping part of the wrapper around said
article.
5. A wrapping machine as claimed in claim 4, wherein the locating
means is adapted to wrap said first part of the wrapper around an
article.
6. A wrapping machine as claimed in claim 3, wherein the locating
means includes heat transfer means arranged to contact an
overlapped portion of the wrapper including said first part.
7. A wrapping machine as claimed in claim 1, including at least two
of said surfaces, said surfaces being spaced so that articles on
said path pass between them and so that different parts of a
wrapper may be contacted substantially simultaneously by said
surfaces.
8. A wrapping machine as claimed in claim 1, including at least one
pusher for advancing a partially-wrapped article along said path,
said pusher including means for sealing an overlapped portion of
the wrapper during conveyance of the article by transfer of heat
between the pusher and said portion.
9. A wrapping machine as claimed in claim 1, including a first
pusher for moving an article along said path, and a second pusher
for moving an article along said path, said second pusher being
arranged to take over conveyance of an article on said path from
said first pusher.
10. A wrapping machine for wrapping articles in succession,
including:
means for conveying said articles in succession and in spaced
relationship along a path,
means for delivering wrappers in succession to said articles,
including means for locating a first part of each said wrapper with
respect to one of said articles moving on said path whereby said
wrapper is associated with an article,
means adapted to cause relative movement of a second part of the
wrapper with respect to the associated article so as to cause the
wrapper to be tightened around at least part of the article,
said means adapted to cause relative movement of the wrapper
comprising means providing at least one surface relative to which
said second part of the wrapper is caused to move during movement
of the article along said path, said at least one surface being
adapted to provide sufficient friction between said at least one
surface and said second part of said wrapper to cause drag on said
second part of said wrapper, and
resilient means for applying pressure between said at least one
surface and said article to increase said drag on said second part
of said wrapper.
11. A wrapping machine as claimed in claim 10, including a support
surface, a movable plate between which and said support surface an
article is movable along said path, and resilient means for urging
the plate into contact with part of a partially-wrapped article on
said path, so that the article is lightly pressed between said
movable plate and said support surface.
12. A wrapping machine as claimed in claim 10, wherein said means
for delivering wrappers is adapted to deliver said wrappers to said
articles at a predetermined position along said path and said
conveying means comprises opposed conveyors downstream of said
predetermined position and adapted to substantially simultaneously
engage successive packets in turn.
13. A wrapping machine as claimed in claim 11, wherein said means
for delivering wrappers is adapted to deliver said wrappers to said
articles at a predetermined position along said path, including
opposed stationary guides arranged substantially downstream of said
predetermined position, said guides being arranged to define an
aperture through which each article and associated wrapper is
conveyed by said conveying means and being spaced so as to cause
initial wrapping of said wrapper around said article.
14. A wrapping machine for wrapping articles in succession
including:
means for conveying said articles in succession and in spaced
relationship along a path,
means for delivering wrappers in succession to said articles,
including means for locating a first part of each said wrapper with
respect to one of articles moving on said path whereby each wrapper
is associated with an article,
means adapted to cause relative movement of a second part of the
wrapper with respect to the associated article so as to cause the
wrapper to be tightened around at least part of the article,
and
a first pusher for moving an article along said path and a second
pusher for moving an article along said path, said second pusher
being arranged to take over conveyance of an article on said path
from said first pusher, said first and second pushers having
complementary shapes to allow each to have simultaneous contact
with different parts of said article.
15. A wrapping machine, for wrapping articles in succession,
including:
means for conveying said articles in succession and in spaced
relationship along a path,
means for delivering wrappers in succession to said articles,
including means for locating a first part of each said wrapper with
respect to one of said articles moving on said path whereby each
wrapper is associated with an article,
means adapted to cause relative movement of a second part of the
wrapper with respect to the associated article so as to cause the
wrapper to be tightened around at least part of the article,
successive conveyors for conveying articles along said path,
including independent drives for each of said conveyors and means
for controlling at least one of said drives so that at least one of
the phase and speed of said conveyors may be varied, so that the
position at which an article is transferred between said conveyors
may be varied.
16. A wrapping machine including means for moving a succession of
spaced packets continuously along a path, and means for delivering
a succession of wrappers across said path at a predetermined
position along said path, in timed relationship to said packets so
that each wrapper is intercepted by a packet and said packet
becomes partially wrapped by said wrapper as said packet and
wrapper move downstream of said predetermined position, wherein
said moving means comprises opposed conveyors substantially
immediately downstream of said predetermined position where the
packets intercept the wrappers, so that each partially wrapped
packet is engaged on opposed surfaces by said conveyors.
17. A wrapping machine, including means defining a substantially
straight path along which packets are moved continuously in
succession, means for delivering a succession of wrappers so that
each wrapper is intercepted by a packet moving on said path, and
means for folding and sealing the wrapper around the packet,
including a first pusher for moving a packet along said path, and a
second pusher for moving a packet along said path, said second
pusher being arranged to take over conveyance of a packet on said
path from said first pusher, and said first and second pushers
having complementary shapes to allow each to have contact with
different parts of said packet.
Description
This invention relates to wrapping machines, particularly for
wrapping cigarette packets in transparent plastics film.
According to one aspect of the invention a wrapping machine
includes means for conveying a succession of spaced articles along
a path, means for delivering a succession of wrappers to said
articles including means for locating a first part of said wrapper
with respect to an article moving on said path, and means for
causing or tending to cause relative movement of a second part of
the wrapper with respect to the article so as to cause or tend to
cause the wrapper to be tightened around at least part of the
article. In a preferred arrangement the articles are packets and
are, for convenience, subsequently referred to as such. Preferably
the locating means is part of the means for conveying a packet
along the path, and may conveniently comprise a pusher which
engages the trailing side of a partially-wrapped packet. The pusher
may also serve to fold said first part of the wrapper against said
trailing side. The means for causing or tending to cause movement
may comprise a surface relative to which the second part of the
wrapper moves, the friction between the wrapper and the surface
being sufficient to create drag which causes or tends to cause
tightening of the wrapper around the packet. The surface may be
stationary or may be moving, e.g. part of the wrapper may contact a
conveyor moving at a speed which differs from that of the packet.
The friction between the surface and the wrapper is preferably
relatively low so that there is no risk of marking or otherwise
damaging the wrapper. There may be more than one surface. For
example, a packet with an enveloping wrapper may pass between upper
and lower surfaces each of which tends to tighten the wrapper
around the packet. It would be possible to apply light pressure
between the surface and the packet to increase the drag effect on
the wrapper.
The use of a slide or other surface to ensure wrap tightness is
particularly valuable during initial wrapping of the wrapper around
the packet. Thus the locating means may be the first fold pusher.
Maintaining wrap tightness is, however, important up to the
position at which the wrapper is finally sealed. Hence, by using
means such as one or more slide surfaces up to and during sealing
of at least the first seam of the wrapper, maximum benefit from the
invention is obtained. It follows that where the wrapper comprises
a thermoplastics material and an overlapped seam of the wrapper is
sealed by heat it is preferred to convey the packet by means of a
heated pusher which contacts the seam while overcoming slight
resistance to motion generated by one or more surfaces such as
referred to in the previous paragraph. An additional benefit gained
in this case is that the slight friction ensures good contact
between the pusher and the seam, so that heat transfer is
facilitated.
According to another aspect of the invention a continuous wrapping
machine includes at least one pusher for advancing a partially
wrapped packet along a substantially straight path, said pusher
including means for sealing an overlapped portion of the wrapper
during conveyance of the packet by transfer of heat between the
pusher and said portion. The sealing may be effected by heating
(e.g. of thermosetting or thermoplastic material, which may be the
wrapper itself or an applied adhesive). In this case the pusher
preferably comprises an electrically-heated element and may
cooperate with means for controlling the electric current to the
element and so maintaining a temperature range acceptable to the
packet and wrapper. It will be understood that in the case of a
thermoplastic material the sealing process is analagous to welding,
the sealed portions being set by subsequent cooling of the
material. With the small quantities of heat which it is generally
necessary to apply, this cooling occurs quickly at ambient
temperature. In principle cooling pushers could be used, e.g. to
cause rapid setting of pre-heated thermoplastic adhesive applied to
the wrapper.
According to another aspect of the invention a wrapping machine
includes means for moving a succession of spaced packets
continuously along a path, and means for delivering a succession of
wrappers across said path in timed relationship to said packets so
that each wrapper is intercepted by a packet, wherein said moving
means comprises opposed conveyors substantially immediately
downstream of the position where the packets intercept the
wrappers, so that each partially wrapped packet is engaged on
opposed surfaces by said conveyors. Said opposed conveyors
therefore preferably engage each partially-wrapped packet
substantially simultaneously. In contrast to prior art systems
where such opposed conveyors (if present at all) are well spaced
from the position at which the wrapper is intercepted by the
packet, this arrangement retains control of the wrapper as soon as
possible after it has been intercepted by the packet and allows it
to be contacted by a surface having a speed related to that of the
packet: this is particularly advantageous in high speed machines
(e.g. machines capable of processing in excess of 400 packets per
minute)
According to a further aspect the invention provides a wrapping
machine having a substantially straight path along which packets
are moved continuously in succession, means for delivering a
succession of wrappers so that each wrapper is intercepted by a
packet moving on said path, and means for folding and sealing the
wrapper around the packet, including a first pusher for moving a
packet along said path, and a second pusher for moving a packet
along said path, said second pusher being arranged to take over
conveyance of a packet on said path from said first pusher, and
said first and second pushers having complementary shapes to allow
each to have simultaneous and/or extended contact with different
parts of said packet. The first and second pushers preferably have
constant speeds, the speed of the second pusher being not less than
that of the first pusher. At least one of the pushers may perform a
folding operation on the wrapper, so that the extended contact with
the packet may be at least partially through a folded part of the
wrapper and so that said contact may help to hold the folded part
in place against the packet. At least one of the pushers may
consist of an element intended to transfer heat to (or from) an
overlapped seam of a wrapper so as to seal the seam and at least
partially complete the sealing of the wrapper around the
packet.
According to a still further aspect of the invention successive
article conveyors in a machine for wrapping articles, which
conveyors have a common path portion, are driven by independent
drive means, whereby by control of at least one of said drive means
the phase and/or speed of said conveyors may be varied,
particularly so that the position at which an article is
transferred between said conveyors may be varied. In this way the
period during which an article is contacted by a conveyor may be
controlled. For example, where the machine is of variable speed and
one conveyor carries a heated pusher for applying heat to a wrapper
to seal overlapped portions thereof, control of the drive means may
allow control of the period so that substantially constant
quantities of heat are transferred irrespective of machine
speed.
Some or all of the various aspects of the invention may be
incorporated in a wrapping machine in any combination. Although the
wrapping machine has been described with particular reference to
packets, the invention is applicable in all aspects to machines for
wrapping or packing other articles (both in and outside the tobacco
industry) and reference herein to "packets" and "wrappers" and
"wrapping" should be construed accordingly. For example, the
invention could be used in the wrapping (i.e. packing) of bundles
of cigarettes, i.e. in a cigarette packing machine, or bars of
soap.
The invention will be further described, by way of example only,
with reference to the accompanying diagrammatic drawings, in
which:
FIG. 1 is a perspective view of a wrapping machine,
FIG. 2 is a side view of part of a modified wrapping machine,
FIGS. 3-5 are transverse sectional views of various pushers in the
machine of FIG. 2,
FIG. 6 is a plan view of another part of the machine of FIG. 2,
FIG. 7 is a part-sectional view on the line VII--VII in FIG. 6,
and
FIG. 8 is a sectional view of a modified machine on a line
corresponding to the line VIII--VIII in FIG. 2,
FIG. 9 is a detail sectional view on the line IX--IX in FIG. 2,
and
FIG. 10 is a view in the direction of arrow X in FIG. 9.
FIG. 1 shows a machine for wrapping cigarette packets in a
transparent film of thermoplastics material.
The machine includes a film reel unit 10 having carriers for two
film reels 12, 14. A splicer unit 16 is provided for joining the
trailing end of the film from the reel 12 in use to the leading end
of the replacement reel 14 (and, alternately, vice versa).
The film web 18 passes from the film reel unit 10 around several
idler and tension rollers to a feed and cutting unit 20. Just
upstream of the unit 20 a tear tape 22 is delivered onto the film
web 18 from a tear tape reel 24. The tear tape 22 passes a hot wax
applicator 26 prior to delivery onto the film web 18. The unit 20
includes a roller 28 and counter roller 29 which together press the
tear tape 22 onto the film web 18 so that they are united by the
hot wax. The roller 28 includes a narrow cutter 31 for cutting the
tear tape 22 and underlying film 18 for producing a tear tab in the
completed wrapper.
The feed and cutting unit 20 includes a pair of feed rolls 32
positioned below the rolls 28, 29. The rolls 32 control the speed
at which the film web 18 and tear tape 22 are withdrawn from the
respective reels 12, 24. Just below the rolls 32 is a rotary cutter
30 which severs successive leading portions of the film web 18 (and
attached tear tape 22) to form wrappers 36. The cutter 30 acts
against a counter surface or edge (not shown) on the opposite side
of the film web 18. Successive wrappers 36 are withdrawn along a
substantially vertical path by a pair of laterally spaced feed
bands 34 cooperating with a similar pair of bands (not shown)
opposed to the bands 34, so that the wrappers are delivered between
laterally spaced pairs of bands. The wrappers 36 are withdrawn by
the bands 34 at a speed which is somewhat higher than the feed
speed of the rolls 32, so that each wrapper becomes spaced from the
uncut portion of the film web 18.
The bands 34 deliver each wrapper 36 into the path of a packet (not
shown) conveyed along a horizontally extending wrapping line 37.
The packets are received on the line 37 on a lower band 40, so that
each packet is advanced by a pusher 42 engaging its trailing side.
The packets are received on the band 40 from a cigarette packing
machine or from an accumulator unit or other handling unit arranged
downstream of a cigarette packing machine. If each packet is
regarded as having two relatively large faces, two relatively
narrow sides and two ends, the orientation of the packets is such
that their faces are horizontal with their ends parallel to the
direction of movement on the line 37 and, as mentioned, the
trailing side of each packet being engaged by a pusher 42.
An upper band 38 is positioned above the downstream part of the
band 40. The band 38 carries pushers 42 arranged to cooperate with
the pushers 42 on the band 40. The timing of the pushers 42 and the
cutter 30 and the relative speeds of bands 34 and bands 38, 40 is
such that each wrapper 36 is engaged substantially centrally by the
leading side of a packet and plunged between the upper and lower
plates 44, 46 located just beyond the path of the wrapper 36
between the bands 34.
The packet thus has its leading side and upper and lower faces
enveloped by the wrapper 36 with free ends of the wrapper extending
parallel to the upper and lower faces of the packet. The upper free
end of the wrapper 36 is engaged by a pusher 50 on an upper band 48
just beyond the plate 44. The pusher 50 folds the upper free end of
the wrapper 36 against the trailing side of the packet and conveys
the packet further along the line 37.
The downstream part of the upper band 48 overlaps an upstream part
of a lower band 52, which runs faster than the band 48. The timing
between the pushers 52 and 54 is such that the pusher 54 engages
the lower free end of each wrapper 36 and folds it upwards against
the trailing side of the packet. The length of the wrapper 36 is
such that the lower free end overlaps the upper free end and serves
to hold it in place (by means of the pusher 54).
An upper heater band 56 carrying electrically-heated pushers 58 has
an upstream part which overlaps the downstream part of the band 52.
The band 56 runs faster than the band 54 and the heated pushers 58
engage the trailing side of each packet over the overlapped
portions of the wrapper 36. During conveyance of the packet by the
pushers 58, sufficient heat is transferred to the thermoplastics
material of the overlapped portions of the wrapper to cause those
portions to become sealed together.
Downstream of the heater band 56 the packets are conveyed on a
lower plain band 60, which runs at the same speed as the heater
band 56 and also supports the packets while they are conveyed by
the pushers 58.
The packets conveyed by the band 60 downstream of the heater band
56 have open rectangular tubular wrapper portions extending
outwards from each end of the packet. Each of these portions has
upper and lower face portions and leading and trailing side
portions. Rotary folders 62, having a higher peripheral speed than
the linear speed of the packets, engage the trailing side portions
and fold these against the ends of each packet. Stationary plough
folders 63 engage the leading side portions and fold these against
the ends of each packet, and also serve to hold the folded trailing
side portions in place downstream of the rotary folders 62. Further
plough folders 64 then fold first the lower face portions and then
the upper face portions of the wrapper over the already folded side
portions.
Downstream of the plough folders 64 each packet passes between a
pair of driven bands 66 which hold the folded end portions of the
wrapper in place and also apply heat from heaters 68 to cause the
end folds of each packet to become sealed and so complete the
wrapping of the packet.
The wrapped packet is delivered from the end of the band 60 to
further processing apparatus, e.g. a boxer or parcelling
machine.
FIGS. 2-7 show parts of a modified wrapping machine. The machine is
similar in many respects to the machine of FIG. 1.
Delivery of wrappers to and along a vertical path 100 is similar to
that of the wrappers 36 in FIG. 1. A lower band 140 carrying
equally-spaced pushers 142 (only one of which is shown) feeds
successive packets 101 along laterally spaced support surfaces 141
and across the path 100 so that the packet intercepts a wrapper 136
and is received between the upper run of a plain band 145 and the
lower run of a band 148 carrying spaced pushers 150 (only one of
which is shown). The bands 145 and 148 extend almost up to the path
100 and serve to engage or grip the leading end of the packet 101
(and wrapper 136) very soon after it crosses the path 100. Clearly,
because of the curvature of the pulleys, it is not possible for the
bands 145, 148 to contact the wrapper 136 immediately after it has
been deflected by a packet 101. For this purpose upper and lower
guides 144, 146 having slightly curved lower leading edges and
defining an aperture only slightly larger than the height of a
packet 101 are provided and additionally ensure good initial
wrapping of the wrapper 136 around a packet. The drive pulley of
the band 145 may be positioned directly below the smaller upper
pulleys, instead of coaxially with the upstream pulley of the band
152: this allows use of a full width pusher 154 (i.e. similar to
the pusher 154A of FIG. 8), since the possibility of interference
with the band 145 is removed.
The linear speeds of the bands 140, 145 and 148 are the same. The
timing of the pushers 150 is such that each engages the upper
trailing portion 136A of the wrapper 136, folds it along the upper
trailing edge of the packet 101 and subsequently holds it against
the trailing side of the packet as it pushes the latter along
further laterally-spaced support surfaces 153 which start
downstream of the short upper run of the band 145. Friction between
the lower portion of the wrapper 136 and the surfaces 153 while the
portion 136A is held by the pusher 150 against the trailing side of
the packet 101 tends to pull the wrapper around the packet and
serves to ensure a tight wrap of the wrapper around the packet.
A lower band 152 carrying spaced pushers 154 is arranged downstream
of the bands 145. The linear speed of the band 152 is higher than
that of the band 148. The pushers 154 are timed so that each
engages the lower trailing portion 136B of a wrapper 136 and folds
it upwards over the trailing side of the packet 101 and overlapping
the previously folded upper portion 136A. The packet 101 is
subsequently conveyed on the surfaces 153 by the pusher 154, which
holds the overlapped wrapper 136 firmly in place around the packet.
The surfaces 153 and the lower surface of the band 148 serve to
contact and maintain control and tightness of the wrapper 136 as
the packet is conveyed by the pusher 154 in a manner similar to
that during conveyance by the pusher 150.
A heater conveyor 156, comprising laterally-spaced chains or bands
with spaced heated pushers 158 extending between the bands,
overlaps the downstream ends of the surfaces 153 and the band 152.
The bands of conveyor 156 are spaced apart by more than the width
of the wrapper 136. The conveyor 156 has a higher linear speed than
the band 152 and the pushers 158 are arranged so that the trailing
side of each packet 101 is engaged by a pusher which takes over
conveyance from the pusher 154 of a packet on the surfaces 153. The
heated pushers 158 engage the overlapped portions of the wrapper
136 and during conveyance of the packet transfer sufficient heat to
cause these portions to become sealed together. The pushers 158
have lateral extensions which pass between upper and lower side
members which improve stiffness of the lower run of the conveyor
156 and serve as guides and prevent vertical movement of the
pushers during their operative runs.
The pushers 158 are electrically heated and have sliding contacts
at their ends which engage stationary side conductors (as indicated
at 159). Electrical current to the pushers 158 is preferably
controlled so as to maintain an acceptable temperature range
(typically 120.degree.-160.degree. C.) at the pushers; this may be
achieved by controlling the voltage at which and the period during
which the current is applied. The pushers 158 have a relatively
high thermal mass.
During conveyance by the pushers 158 the upper portion of the
wrapper 136 and packet 101 are under control of a stationary
surface 157. The wrapper portion covering the upper face of the
packets 101 may be contacted directly by the surface 157. However,
it is preferred to resiliently press the packets onto the surfaces
153. For this purpose presser members 180, better shown in FIGS. 9
and 10, are attached to the underneath of surface 157 and have
light springs 182 urging them into contact with the packets, which
are thus lightly pressed down onto the surfaces 153. Although the
lower surfaces of the presser members 180 (of which there may be
four in series along the length of the operative run of the pushers
158) and the surfaces 153 are of relatively low-friction material
(e.g. stainless steel), the slight additional friction caused by
pressing on the packets ensures good contact between each pusher
158 and a packet. The members 180 (or the surface 157) and the
surfaces 153 create drag which helps to maintain wrap tightness
during conveyance of the packets 101 by the pushers 158 up until
the seal is complete.
At its downstream end the heater conveyor 156 overlaps a further
lower band conveyor 170 carrying spaced pushers 172. The conveyor
170 has a higher linear speed than the conveyor 156, so that
conveyance of packets is transferred from the pushers 158 to the
pushers 172.
The ratios of the speeds of conveyors 140 (and 145 and 148): 152:
156: 170 are approximately 1: 1.20: 1.33: 1.40. The spacings
between packets (and the pushers on the respective conveyors) are
therefore in the same ratios. Each of the conveyors 140, 148, 152,
156, and 170 has four equally-spaced pushers.
It may be an advantage to reduce or eliminate the speed
differential between one or more of the successive pairs of pushers
150, 154, 158, 172, and hence between their respective conveyors,
so as to reduce impact on the packet 101 and possible consequent
slipping of the wrapper 136 relative to the packet. This may be
particularly useful at the first transfer, between pushers 150 and
154. In this instance, having conveyors 148 and 152 running at the
same speed (which would involve reducing the pitch between pushers
154 to that between pushers 150) would have the further advantage
of potentially maximising the period during which the packet 101
and wrapper 136 are dragged over the surfaces 153 and therefore
also potentially maximising the benefit this has on wrap tightness
and control.
Each of the conveyors 140, 148, 152, 156, 170 comprises timing
bands (or belts) and use of these, as opposed to chains, provides
greater compliance, and hence also potentially helps to reduce
impact on the packets 101. Bands have the further advantage over
chains that they can be used to contact the wrapper 136 directly
and for control of the wrapper and packet 101, e.g. as by bands 148
and 170, and further allow the possibility of transition between a
surface on which the packets slide (e.g. surfaces 153) and a
surface (e.g. of band 170) on which the packets are directly
conveyed.
The pushers 142 and 150 are of generally plain rectangular
sections, as indicated in FIG. 3. The pushers 154, 158 and 172 are
of complementary shapes, as indicated in FIGS. 4 and 5, intended to
facilitate transfer while allowing adequate contact with the
packets, although each of these may similarly be of plain
rectangular shape similar to the pushers 142, 150. Note that during
transfer between pushers each packet is contacted by both pushers
for a short period (or for a longer period if the speed
differential is substantially eliminated).
A continuation of the surfaces 153 may extend to the left as shown
in FIG. 2, so that the conveyor 170 may be set below the
continuation surface in the same way as the band 152 is below the
surfaces 153. (The conveyor 170 may preferably comprise a single
central band for this purpose instead of the laterally spaced bands
as shown in FIG. 6.) Further, an upper slide surface 149 (which
could comprise laterally-spaced portions) may be provided in the
vicinity of the band 148 so that the pusher 150 extends below it
but the surface is below the lower run of band 148 so that it
contacts the wrapper 136 on a passing packet 101. The conveyor 148,
surface 149 and/or pushers 150 may have laterally-spaced portions
to achieve this. The surface 149 would therefore be at
substantially the same level as the surface 157. The slight
additional friction between the portion of the wrapper 136 around
the upper face of a packet 101 and the stationary surface below the
band 148 may further assist wrap tightness and control. It may be
preferable for the upper control surface 149 to start at or
downstream of the position at which pusher 154 first contacts a
packet 101. The surface 149 may extend beyond the downstream pulley
of band 148 to maintain control of the upper portion of the wrapper
136 as far as possible up to the path of the heated pushers
158.
Referring now particularly to FIGS. 6 and 7, which show a part of
the machine mostly downstream of the part shown in FIG. 2, the
conveyor 170 moves packets between rotary folders 162 for forming
the trailing side end folds of the wrapper. The folders 162 have
spaced upper and lower elements 161 (FIG. 7) which, during rotation
of the folders 162, respectively pass above and below stationary
folders 163 for forming and retaining the leading side end folds
and for retaining the trailing side end folds. The folders 163 have
lead-in guides 163A extending between the elements 161 of folders
162. The trailing curved faces of the folders 162 serve to hold the
trailing side end folds in place until the stationary folders 163
take over. This effect may be enhanced by replacing the folders 162
with short belts carrying folder or tucker blocks having upper and
lower elements similar to elements 161. The action of the folders
162 could be assisted by air jets: these could be stationary or
could be carried by the folders 162 themselves. Stationary plough
folders 164 complete the lower and upper face end folds. Operation
of the folders 162, 163 and 164 is substantially similar to that of
the folders 62, 63 and 64 of the machine of FIG. 1.
Downstream of the folders 164 side plates 165 hold the folded ends
of the wrapper in place during transfer of the packet from the
conveyor 170 to opposed conveyor bands 166 which contact the
opposite end folds of each packet. The bands 166 are heated by
heater blocks 168, which contain electrically-heated cartridge
elements, so that the end folds are sealed during passage of the
packets between the bands. The material of the bands 166 may
typically be steel or PTFE-impregnated glassfibre, the material
being selected to have adequate thermal conductivity and resistance
to the effects of relatively high temperatures. The heater blocks
168 could comprise separately heated sections (as indicated in FIG.
6) to allow greater control of heat applied to the bands 166. One
or more of the sections could be retractable and the sections or
blocks 168 could be spring-loaded towards the bands 166 (as
indicated at 168A in FIG. 6). This ensures reasonably constant
pressure between the blocks 168 and the bands 166 and also between
the bands and the packets; and helps to accommodate slight
variations in pack length (between ends). The heater blocks 168
could be replaced or supplemented by radiant, e.g. halogen,
heaters. Heat may be transferred to (or, exceptionally, removed
from) the return runs of the bands 166, to aid temperature
control.
It will be understood that each of the conveyors 140, 148, 152,
156, 170 may have a backing member adjacent its operative run to
support the conveyor. This may be particularly beneficial where the
conveyor bears directly on the conveyed packet 101 (e.g. conveyor
170 as shown in FIG. 2 and conveyor 148 in the absence of surface
149). Theoretically the backing member need not be straight. For
example, if the pulleys of the conveyor 148 were set higher than
shown in FIG. 2 the operative run of conveyor 148 could be
displaced downwardly by an initially convex backing surface
arranged to move the pushers 150 progressively into their operative
positions. When the surface 149 extends for only part of the length
of the lower run of conveyor 148 then the downstream pulley 151 may
be set at a slightly higher level than the upstream pulley 155 and
the backing member may be initially parallel to the surface 153
(i.e. for some distance downstream of pulley 155) and then be
angled upwards slightly towards the pulley 151, thereby guiding the
downstream portion of the lower run of conveyor 148 above the
surface 149. The pushers 150 preferably contact the wrapper 136 and
packet 101 directly from the pulley 155 with no deflection of the
lower run of the conveyor 148, at least upstream of the surface
149.
One advantage of the machine is that no adjustment of the packet
conveying conveyors is necessary for change in packet width (i.e.
between sides of the packet), since timing is by reference to the
trailing side of a packet. Changes in packet length may also be
relatively easily accommodated, e.g. by moving apart laterally
spaced bands. The effect on the machine of changes in packet height
(i.e. between faces) may be reduced if it is arranged that
adjustment of stationary as opposed to moving parts is required.
Thus, referring to FIG. 8, which is a sectional view of a slightly
modified arrangement on a line corresponding to the line VIII--VIII
in FIG. 2, the surface 153 is moved vertically to adjust its
distance from the lower run of conveyor 148 (and from surface 149).
The positions of the conveyors 148 and 152 remain unchanged. Note
that the height of the top of the pusher 154A above the diameter of
downstream pulley 174 around which conveyor 152 passes is small
(e.g. 3 mm): this reduces acceleration of the packet on surface 153
as the pusher rounds the pulley at the end of its operative
run.
At least some size changes could be automated. Sizes, or codes
referring to known packet sizes, could be keyed into a control
microprocessor. Alternatively a reference packet could be
monitored, e.g. by opto-electronic sensors incorporated on or
adjacent the machine, so that a control system sets appropriate
size-related adjustments on the machine following monitoring, e.g.
following insertion of the reference packet into a monitoring
pocket in which it is monitored. Further sensors at the monitoring
position could cooperate with corresponding sensors for packets
after wrapping to ensure equivalence: this feature could also be
used with a packing machine where it could serve to check that the
packet being produced had the same printing etc. as the reference
packet.
It will be appreciated that the relative timing of the conveyors is
critical, particularly where conveyance of packets is transferred
between conveyors. The conveyors may be driven from a common prime
mover with appropriate gearing. Alternatively, independent drives
which are electrically controlled to maintain timing may be used.
In the machine of FIGS. 2-7 a combination of these is used. The
trailing pulleys of conveyors 148, 152, and 156 and leading pulleys
of conveyors 140 and 145 are driven from a first common prime
mover. A second common prime mover drives the leading pulleys of
conveyor 170, the trailing pulleys of bands 166 and the rotary
folders 162.
An advantage of providing independent drives is that where
conveyors overlap the position at which the downstream conveyor
takes over conveyance of the packet may readily be controlled by
adjustment of the relative phasing of the drives to alter the
relative positions of the pushers of the respective conveyors. This
would be much more difficult with conventional drive arrangements
where each conveyor would be linked to a common prime mover. Thus,
in the case of conveyors 156 and 170 for example, these conveyors
may be arranged to be independently driven and to overlap by a
rather greater amount than shown in FIG. 2. Then the relative
phasing of the drives may be altered (during a period when the
machine is idle), so that pusher 172 takes over conveyance of
packets 101 from pusher 158 earlier or later. In this way the
period during which the packet 101 is contacted by a heated pusher
158 may be adjusted. This is a useful facility, particularly where
the machine may be run at variable speeds, since it may be possible
in this way to maintain the period of contact with the pusher 158
relatively constant at different machine speeds or otherwise to
control this period as required. It is also possible to easily vary
the relative speeds of successive conveyors having independent
drives but this would normally require replacement at least of one
of the conveyors since the spacing between pushers of a conveyor is
related to conveyor speed, i.e. the pitch between packets varies
with speed of conveyance.
It may be noted that a slight speed error may occur during the
period when the pusher 142 is still in contact with a packet 101
and starts to move around the downstream pulley of conveyor 140.
One way of overcoming this problem is to control the speed of
conveyor 140 so that it is slightly slowed during this period to
compensate for the otherwise increased speed of the packet. Clearly
the use of an independent electronic drive for the conveyor 140
facilitates this. An alternative way of dealing with the same
problem would be to provide the pusher 142 with a leading surface
which slants backwards from the conveyor. Another possibility would
be to use a so-called tip-back pusher conveyor or, more simply,
provide parallel belt conveyors with links between them to keep the
pusher vertical. It may even be possible to arrange for the
conveyor 140 to move slightly slower than the conveyors 145 and
148, so that as soon as a packet is gripped by these latter
conveyors it is moved away from the pusher 142. The problem may be
reduced without recourse to speed adjustment or a relatively
complicated pusher construction by minimising the height of the
pusher above the effective diameter of the downstream pulley, as
mentioned above with reference to FIG. 8.
* * * * *